DESCRIPTION: U01 - Cohort Study with Young Men of Color who have Sex with Men In this fourth decade of the HIV epidemic, we continue to see 50,000 new infections annually in the U.S., particularly among Black/African American and Latino young men who have sex with men (YMSM of color), who now account for 60% of new infections among Black/African American MSM and 45% of new infections among Latino MSM. Black/African American YMSM remain five times more likely to be HIV seropositive, seven times more likely to have an undiagnosed HIV infection, and 45% more likely to be diagnosed with an STI than other YMSM. YMSM of color are also the least likely to seek and remain in HIV/AIDS care, and when they do seek care, they typically already have advanced HIV disease. Among youth who initiate antiretroviral therapy (ART), 54% will achieve viral suppression; unfortunately 57% will not be retained in care and less than 6% will remain virally suppressed. Changing the course of this epidemic is going to require a dramatically different approach to prevention. We are therefore proposing to conduct longitudinal research with a large and diverse cohort of 450 YMSM of color in order to prevent new HIV infections, reduce transmission, and reduce HIV/AIDS-related disparities by focusing on successful engagement in care. Building on the HIV Continuum of Care and Prevention paradigm (i.e., seek, test, treat, and retain in care) and the Syndemic Theory of Risk, we will use a mixed-methods study design to collect and analytically triangulate quantitative, qualitative, and biological measures at baseline and every six months. Participants will be recruited from public venues, HIV test sites, and HIV/AIDS clinics using randomized probability and purposeful sampling designs. All participants will be tracked to ensure a retention rate of 90% or better, which is a feasible target given our retention rates of 94% in the Healthy Young Men's (HYM) Study. The specific aims are to 1) better understand and operationally define what linkage, engagement, retention to care (both primary health and HIV/AIDS treatment) and adherence means to HIV- and HIV+ YMSM of color; 2) characterize and monitor over time YMSM of color's use of alcohol and illicit drugs; utilization of HIV testing and prevention services; incidence of HIV and STIs; insurance status and access to health care services, including primary care and HIV/AIDS treatment services; engagement in and utilization of health care and HIV/AIDS treatment services; retention in HIV/AIDS care and adherence to ART; and utilization of biomedical interventions, such as PrEP and PEP; and 3) identify barriers/facilitator of engagement along the HIV Continuum of Care and Prevention. The proposed research builds on close to two decades of NIH-funded research by our team focused on this and other high-risk youth populations.